In general terms, the main research conducted in this proposal is directed toward a better understanding of the action of narcotic analgesics and the development of tolerance and physical dependence to these drugs using laboratory animals. More specifically, the proposal concerns 1) the role of biogenic amines on narcotic tolerance and efficacy of narcotic antagonists, 2) effect of narcotics on the transport of amino acid precursors of putative neurotransmitters into the brain, 3) characterization of the narcotic receports in the guinea pig ileum and 4) characterization of the narcotic receptors in the guinea pig ileum and 4) characterization of the narcotic respiratory receptor. BIBLIOGRAPHIC REFERENCES: Huang, J.T. and Takemori, A.E.: The accumulation of etorphine by slices of cerebral cortex and corpus striatum of rats. Biochem. Pharmacol. 25: 47-51, 1976. Tulunay, F.C., Yano, I. and Takemori, A.E.: The effect of biogenic amine-modifiers on morphine analgesia and its antagonism by naloxone. Eur. J. Pharmacol. 35: 285, 1976.